Research Projects

Neuroethology of navigation in the sea slug Tritonia diomedea

Navigation is a key behaviour performed by all motile animals.
We work with Tritonia because this slug is amenable
for a variety of experiments (both behavioural and neurophysiological)
that allow us to test the role of single neurons
in
navigational
behaviours. Like most animals, Tritonia is primarily
concerned with mates, prey and predators. Tritonia navigates
relative to these targets using odours, water
flow, and possibly the earth's magnetic field. Our long term
goal is to understand how these different sensory cues are integrated
together to produce the coordinated responses we see as the animals
seek out food and possible mates, while avoiding predators. We
plan to tackle this problem use several approaches:

Controlled experiments in the laboratory testing the animals' behavioural
responses to different aspects of the sensory cues (odour pulse
concentrations and durations, water flow directions, speeds and
variability). e.g. Wyeth and Willows 2006B | McCullagh Poster

Neurophysiological experiments exploring the connection between the chemosensory
organs that detect odours, rheosensory organs that detect flow,
and the motor neurons that control turning. e.g. Wyeth
and Willows 2006B.

Sensory systems are a key component in the control of most behaviours.
At present, our understanding of gastropod sensory systems is
limited. Previous research on the peripheral nervous
system has created a patchwork of information encompassing different
sensory cell types scattered across different species. Our goal
is to map the sensory cells present in the lips
and tentacles of Lymnaea
stagnalis as well as the siphon of Aplysia californica. We plan to create a catalog of sensory cell types and
then match those types to their
modality (mechanosensory or chemosensory). Our approaches here
include:

Immunohistochemical, backfill, and vital dye labelling of sensory
neurons to provide both anatomical information as well as putative
neurotransmitter(s) for each sensory
cell type
Poster

Behavioural experiments to test the roles of different sensory cell types/neurotransmitters
in different behaviours

Physiological experiments (optical recordings) from sensory cells to
test their responses to mechanical and chemical stimuli

The Snail Lymnaea

A backfilled Lymnaea tentacle

Neurotransmitters in Hermissenda statocysts

The vestibular organs in gastropods are statocysts. These have been studied extensively in Hermissenda crassicornis to understand the cellular mechanisms of learning. The sensory hair cells in the statocysts are known to use the neurotransmitter GABA in synapses with eye photoreceptors. However, the hair cells likely also contain a number of other neurotransmitters of unknown function. For example, we have evidence histamine is also present in most of the hair cells. We plan two approaches to study this complexity:

Immunohistochemical labelling to identify putative neurotransmitters in the statocysts. Poster

Behavioural experiments to explore the range of responses to different vestibular stimuli, as well as pharmacological manipulations of the putative neurotransmitters to test their roles in the different responses.

The nudibranch Hermissenda and two views of its brain, showing the eye (e) and statocyst (s).

Navigational strategies for finding odour sources

Many animals use odour-gated rheotaxis to find odour sources. In other
words, the animals head upstream when they detect an attractive
odour. This strategy is successful because it is the flow that
transports the odour from the source to the animal. However,
how do animals cope with flows that vary in direction such that
they could be led astray? One possibility
might be to use a magnetic compass
to follow the last-known heading from which odour was detected
to reach the source. Our goal is to explore this possibility
using:

Slugs with a magnetic compass (black) are better at finding an odour
source than those that simply head upstream (blue)

Lobster navigation and bait preferences.

Lobster navigate using odours and waterflow, and fisherman exploit this by baiting their traps to attract the lobsters. However, little is known about optimal bait types and the important odour found in plumes that attract lobster. Our goal is to build understanding of lobster responses to bait by:

determining bait preferences for lobster in a flow-tank that generates realistic odour plumes

analyzing chemical constituents of bait for their attractiveness to lobster

We anticipate our results will be useful for lobster fisherman attempting to improve the cost-effectiveness of their bait use.Collaboration
with Jim Williams

Biofouling and Antifouling Coatings

Biofouling, or the growth of organisms on man-made surfaces, affects many industries: food production, oil and gas, and shipping, among many others. As part of the StFX Centre for Biofouling Research, we are exploring novel non-toxic options for reducing biofouling, particularly focused on cold water marine habitats. The WyethLab's role is primarily involved in field surveys of biofouling and field tests of candidate coatings that may reduce biofouling. Current projects include: